Suncor 'turns corner' on tailings

Patented new technology creates quick-drying material in days -- and ends the need for massive new oilsands ponds
Author: 
Dave Cooper
Source: 
edmontonjournal.com
Date published: 
Sat, 2010-10-02

Standing on the lip of Suncor Energy's Millennium mine, the vista can take your breath away.

Fifty to 100 metres below, seven giant shovels positioned around the gaping, 15-square-kilometre pit fill a parade of 400-tonne trucks, each carrying the equivalent of 200 barrels of bitumen.

It's the kind of scene that makes dramatic photos: a surface mine before reclamation, a barren, rocky landscape interlaced with haul roads.

And it's an example of the image that shocked Hollywood director James Cameron into calling the oilsands a "black eye" on Canada's environmental record before his trip to the area this week.

But starting next year, the scene will begin to change as a river of sand begins to fill the mine from the outer circle, a virtual doughnut of material moving toward the centre.

"We want to put the sand back in the pit as we go. The mine will become a sand dump, with the (fine clay tailings) running off into a catchment basin and pumped out," said Anne Marie Toutant, Suncor's vice-president of mining and reclamation.

Using its new patented tailings reduction operation (TRO) technology, Suncor will store the liquid material in its new South Tailings Pond -- the only one it will operate in the future. The oilsands firm has eight tailings ponds; a ninth, its original Pond 1 -- built in 1967 -- was declared reclaimed last week.

After three years, the pumped-out material will have transformed into mature fine tailings (MFT), composed of clays and unrecovered bitumen. Left alone, it could stay as a yogurt-like mass for centuries.

But once fed into the TRO system, it be will converted into a quick-drying, porridge-like material within days.

"This year has been a big one for us. We have turned the corner," said Bradley Wamboldt, director of tailings-reductions operations.

"In 2009 we had 30 hectares for drying, but this year we have 350 hectares in various locations around the site," he said, standing on a dike overlooking the 50-hectare Pond 6.

Using TRO, Suncor will soon be able to treat 30,000 tonnes of MFT a day. But the process doesn't work in freezing weather, so it's operational for only eight months a year. And Suncor produces 25,000 tonnes of new clay tailings each day, with production continuing to increase.

"As we expand TRO, we expect to be treating all our tailings beyond production by 2013. Then we will be consuming our legacy tailings."

And there are plenty available. Suncor has 200 million cubic metres of MFT stored in the 40 square kilometres of ponds, but by 2018 most will be gone.

"We'll will be working at reclaiming our last large one by then, and there won't be much after that because we aren't building any new ones," Wamboldt said.

The firm has already spent $250 million on TRO research, and expects it will cost another $1 billion to completely install the system by 2013.

But that is really no more costly than the previous system.

"In the old plan we were planning to build Ponds 8, 9, 10, 11 and 12. None of those will be built," said Wamboldt. It would have cost Suncor about $1 billion to build and maintain that many new ponds.

Until 1998, Suncor was simply stockpiling its tailings -- and building new ponds to hold them.

That year it began using a system called CT (consolidated tailings), in which gypsum and sand were added to speed settling, building up a solid base from the bottom of the pond.

But the process was slow and complicated compared with TRO, which first appeared in field tests in 2008. All CT operations will shut down next year.

"The challenge for the oilsands from the tailings perspective is mature fine tailings. Everything that is not bitumen is tailings -- the sands, clays and some residual bitumen," Wamboldt said.

"The coarse material drops out, the clear water rises to the top, but then you get this material that stays in the middle that consolidates to about 30 per cent solid and may stay like that for hundreds of years."

So under TRO, that material is pumped out, mixed with a polymer used by the sewage industry to clump material together, thus allowing the water to escape.

On Pond 6, a floating dredge works on one side, with pipes passing through the polymer-adding unit and spewing out the thick, grey, porridge-like tailings on the other side, slowly filling in the pond. The excess water immediately flows down the beach in rivulets, back into the pond.

As the tailings ponds disappear, Suncor will be able to speed up reclamation. And set a new standard for its new mining areas.

"Our Pond 1 was begun in 1967 (and closed in 1980) and now is reclaimed, so that's 40 years of disturbance.

"With TRO, there will be just 10 years of disturbance," Wamboldt said.

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EXTRACTING BITUMEN

From the moment the oil-soaked sand is carved out of the mine, it may be only a matter of hours until the bitumen it contains is processed, upgraded and sitting in tanks to be sent by pipeline to refineries across North America.

At Suncor's Millenium Mine, massive trucks lumber up a ninekilometre haul road and drop their loads into a crusher, which breaks up the largest chunks, adds warm water and sends the slurry by pipeline to the separator.

Injected into the middle of a cone-shaped primary separation tank several storeys high, the sand falls to the bottom and the oil rises, where it slowly flows over the sides like coffee in an overflowing cup. Up to 92 per cent of the bitumen is recovered this way. Two further stages extract another four per cent of the bitumen. The remaining four per cent joins the tailings flow.

Suncor's Tailings Reduction Operations (TRO ) promises to speed up reclamation. Beginning next year, tailings from the separation plant will be piped to the mined-out areas of the Millennium Mine, allowing the coarse sand to build up in sloping areas. The liquid fine tailings will flow into the new South Tailings Pond, where it will settle to form mature fine tailings over three years. This yogurt-like material will be dredged, combined with a polymer and piped to a beaching area where the now porridge-like material will be deposited in layers, allowing the excess water to run off and be collected.

The clay surface will be solid enough to support vehicles in a matter of weeks.

 
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